The present invention relates to an air conditioner system for a vehicle, and particularly, to an apparatus for controlling a cooling fan of a condenser in an air conditioner system including a variable volume or displacement compressor.
In general, a condenser and a radiator are disposed side by side in an air conditioner system for a vehicle and cooled by air flow produced by a common fan driven by an electric motor and by relative air flow produced by forward motion of the vehicle.
The control of operation of the cooling fan is required to be conducted on the basis of the demand of both the air conditioner system including the condenser and the engine including the radiator. One example of such controlling device is known from Japanese Patent Application Laid-open No. 67918/83.
This controlling device comprises a heat-sensitive switch adapted to be operated when the temperature of the cooling water in the radiator exceeds a predetermined level, and a pressure-sensitive switch adapted to be operated when the pressure of a refrigerant in the condenser exceeds a predetermined level, so that the operation of either one of the heat-sensitive and pressure-sensitive switches causes the cooling fan to be started, thereby preventing the over-heating of the engine and/or the over-load of the compressor.
When a variable volume or displacement compressor is used as the compressor of the air conditioner system, the control of the cooling fan suitable for the actual load of the variable volume compressor cannot be performed. It is difficult to maintain the temperature of the refrigerant at an appropriate value merely by using only the pressure of the refrigerant as the detected variable to produce a detection signal on the air conditioner system side as in the above prior art control apparatus.
The present invention has been accomplished with the above circumstances in view. It is an object to provide a cooling-fan controlling apparatus capable of driving a cooling fan in accordance with a value of the actual load of a variable volume compressor.